The invention relates to filter assemblies.
A filter assembly typically comprises a housing having an inlet and an outlet. A filter element is located within the housing and communicates with the inlet and the outlet. Accordingly, fluid entering the inlet is filtered by the filter element before leaving through the outlet. A typical filter element may be of hollow cylindrical shape.
It is a problem that many filter elements currently manufactured have a comparatively small flow capacity. This means that, in many applications, it is necessary to use a significant number of filter elements connected in parallel in order to provide a required flow of fluid. For air filters, this leads to a limitation imposed by the pressure drop through the core. In addition, the use of a large number of small filters requires the use of larger housings with resultant increased cost and space requirements.
According to a first aspect of the invention, there is provided an air filter assembly comprising a housing having an inlet and an outlet and containing at least one filter module, the at least one filter module including a filter element communicating with the inlet and the outlet such that fluid entering the inlet is filtered by the filter element before leaving via the outlet, the filter element including a pleated filter membrane of hollow cylindrical shape having a pack height of 12 mm or less and an air throughput of at least 1300 normal m3/hr per 250 mm of the axial length of the membrane at an inlet pressure of 2 barg.
According to a second aspect of the invention, there is provided a system comprising an air supply, a filter assembly according to the first aspect of the invention and in which the filter membrane is a sterilizing grade filter member with the inlet of the filter assembly connected to said supply and the outlet of the filter assembly connected to processing means which receives sterile air from the filter assembly for use in a process, means being associated with the filter assembly for water intrusion testing the filter membrane in situ.
According to a third aspect of the invention, there is provided a method of supplying sterile air to processing means comprising passing air through a filter assembly according to the first aspect of the invention and in which the filter membrane is a sterilizing grade filter membrane feeding air from the filter assembly to said processing means, and periodically halting the flow of air from said filter assembly and water intrusion testing the filter membrane in situ.